Interesting review suggests there are differing versions of firmware and long breakin needed:
I had the same experience the first time I listened to my mhdt Havana Balanced DAC. With some experimentation I quickly learned a few things that change my satisfaction dramatically. First, the stock GE 5670 buffer tube sounds bland and perhaps this is a good way to ship mhdt DACs because the stock tube will be forgiving in any system. But better to change it. You'll see in mhdt's literature a long list of alternate tubes to try. I found the Bendix or Tung-Sol 2c51 and the Bendix 6385 to open up and enliven the DAC in a big way.
Next, like many things digital, these mhdt DACs are very sensitive to what they are resting on. My custom racks are solid maple but the Havana Balanced doesn't sound convincing sitting on any surface on its own feet, in my experience. After many trials, Aurios media bearings under it were transformational to the DAC's sound, giving it explosive dynamics where appropriate, beautiful and dense tone, and remarkable definition.
I also found some PCM56K chips to give it further improvements in definition, tone and spatial projection, over the stock J versions. These are cheap.
Last it takes some time to burn-in/break-in. But clearly resting the Havana Balanced on Aurios media bearings was the single most significant improvement. It was transformational even with the stock tubes and chips. I'm pretty sure Herbie's Tenderfeet will also work well for less. Magnetic levitation did not help. Sorbothane made everything worse. Brass cones were the next best resting method to bearings. I think any bearings-based footer is the right way to go with an mhdt DAC.
The Stockholm is the Havana DAC with a 24/192 input receiver. I should add that I haven't yet moved to computer file audio and while I have fiddled with the USB input on my Havana Balanced, my definitive listening as been via SPDIF input from optical disc. What input are you using? I think many mhdt DAC owners find a USB>SPDIF converter, even just a HiFace or mhdt's own, to be preferable to the mhdt USB input natively built into their DACs.
These mhdt DACs can sound beautiful, organic and wonderfully dimensioned. Upgrading internal capacitors can take things further. But out of the box, it takes some effort to put them in their zone.
Phil, thank you for your excellent advice on the Stockholm. I presume this is the DAC you are currently using? Can you direct me to where you purchased the PCM 56K chips and how many are required. I'm willing to invest some time and money to get this DAC to a new level. Its surprising that as a stock unit it is far from satisfying. I owned the stock Havana and liked it right out of the box. Thanks again
I have two Havana Balanced DACs, one each in my primary and secondary systems. I have heard the Stockholm but it had no advantage on 16/44 material via SPDIF and don't care about USB. I didn't hear any advantage to Stockholm Balanced over Havana Balanced for CD and CD-ripped files, so I didn't bother upgrading. When I do add a file server, if I decide on USB instead of network streaming, I'll go with a USB>SPDIF converter.
For high-res, it makes no sense to me to ingest 24/192 via the receiver but drop bits processing that material at 16/XX in the DAC chips. On the other hand, I haven't heard delta-sigma based DACs capable of high-res, sound as convincing on 16/44 as Havana Balanced, so it looks like I'll end up with two DACs at some point if I continue to prefer the Havana Balanced. It is exceptional at making 1980s & '90s CDs listenable, too.
I got my PCM56P-K (Malaysia) chips from Mouser, online. They are reliable, no risk of fakes. These things are cheap. You need two for a single-ended Stockholm; four for a Stockholm Balanced, same as Havana.
You can find a 145+ page thread on head-fi.org filled with information from chronic modifiers who really tear into these DACs. It's a fully productized design built to a price point so parts upgrading opportunities are rich. Without going overboard you can certainly gain from spending some cash to replace the output coupling caps to V-Cap Copper-Teflon or Dueland. That would be true for most DACs. But if you want to keep upgrades to tubes and chips, avoid soldering, and end up with a beautiful, lively DAC, then either buy several of the alternate tubes to trial for your own decision, or if you tell me how you want to move the sound, I will be happy to direct you to a specific tube that will help. But most of all, get media bearings of some type under that Stockholm, under the feet, not the bottom plate itself. That's the biggest no-pain gain and it's really remarkable for its results.
Everything I've discussed that works for Havana works for Stockholm. I'll also say that I think the Balanced versions of these DACs are well worth the price difference, even if you have to use XLR>RCA converters to connect their balanced outputs to RCA inputs on a preamp. There's a lot more tone and shove in the Balanced versions via balanced outs. As mhdt points out, the single-ended output of a Balanced version is the same as using a single-ended Havana or Stockholm. Well, there are a couple of small exceptions, not least of which is that the unbalanced mhdt DACs often have PCM56P-L chips, while Balanced versions ship with PCM56P-J. If your Stockholm has L chips then you will hear a larger improvement from K chips than I did over my stock Js. I realize your DAC is single-ended as you wrote at the outset. There's a v2 of Stockholm coming soon, and Havana Balanced can still be bought now. If you want the most from your single-ended DAC without radical surgery, then chips, tubes, bearings and burn-in should get you smiling.
Another thing to note is that the single-ended mhdt DACs output 1.1v, lower than the CD standard 2v which is the marker for digital gear. Since most systems have excess gain in the preamp, it's not a problem. But if you are coming to Stockholm from a CD or universal optical player, then Stockholm may sound anemic to you at same position on your volume control. If that's the case, turn it up! The Balanced version of Havana & Stockholm output 2.6v. Also, there is some unconfirmed chatter out of mhdt that Stockholm v2 will have higher output, somewhat above CD standard even in single-ended form.
I'm not sure why you are having such a different experience than with your Havana. I listened to a friend's Stockholm right out of the box and on 16/44 material it duplicated my starting experience with Havana Balanced. Depending on where you live, it could be since you took delivery in a cold weather month that break-in of the electrolytic and other caps simply will take longer. It could be that your Havana had J chips and this Stockholm has Ls. It could be just sample-to-sample inconsistency. Hard to say without being there. Which input are you using? Are you getting the same result from 16/44 and high-res or are you happy with one but not another?
In any case, if you're using USB, my own bias is that an Audiophileo 2 or similar converter will deliver to the SPDIF input a much lower jitter source and wake up your DAC.
I picked up a modded Havanna, based on Sean Caseys reommendaton after listening to yours last spring. This is a fantastic DAC. Mine has thefollowing mods:
1) The replacement of the two input capacitors with Jensen copper foil paper in oil in aluminum case ones.
2) The replacement of the cap behind the input caps with a Jupiter HT.
3) The replacement of the two output coupling caps with Jupiter HTs.
4) The conversion of the RCA coaxial input connector to a BNC connector for true 75 ohm compatibility (I will include a BNC to RCA adaptor).
5) The substitution of a Hi-Fi Tuning Fuse for the stock fuse.
6) The substitution of the stock tube with a Western Electric JW396A/2C51.
I did not do the mod's as the previous owner had it done. I am also now curious about the DAC chips. I need to pop the top and see which ones are in it.
In the positive feedback review they mention the following about replacing the dac chips with AD1856.
"Mhdt designed the Havana so it would delight tweakers everywhere: Jiun-Hsien told me that There is a secret that we only tell Havana users, that if they want to they can replace the stock PCM56P chips with AD1856 chips (which are pin to pin compatible), without changing any components in the Havana DAC. We assembled the Havana with IC sockets for the two PCM56P chips. We purposely installed these two IC sockets so that Havana users could experiment with further possibilities if they wished, like the AD1856 chip, or others."
Did you ever try the AD1856 in your Havanna? If no, do you know anythin about it?
Yeah, Sean likes the Havana! I have the Balanced version, and I recently bought a second one for my Druids system.
The Balanced Havana comes stock with PCM56P-J, which people seem to agree is a slight improvement over the PCM56P that comes stock in single-ended Havana. I went further and replaced the J chip with Malaysian PCM56P-K, from a trusted source (Mouser) and there is no question these improved resolution a bit, have a more spatially rewarding presentation, and firmed up the bass resolution and quality audibly. I now have moved this DAC to my Druid V system.
In my Def4 system I installed the more recently-acquired Havana Balanced, and swapped out the stock chips with AD1856. Keeping in mind that the Balanced Havana sounds meatier and more tone-dense than single-ended Havana (and of course I have to buy 4 chips), the AD1856 is a different sound still within Havana strengths. On other forums, there's been some criticism about the AD1856 making Havana sound "electronic." I don't agree with this -- I can usually trace that criticism to associated gear and to headphones. AD1856 chips give the Havana more resolution, somewhat leaner more truthful (less euphonic) bass, and lays out a more precise soundstage and placements.
It's not shape-shifting or revolutionary, but there's a little less of the boomy, bursty fun of the PCM56P-J or K. You retain the basic tonality strengths of this circuit. Again, to get the best sound you have to rest these DACs on the right footers. I've tried a lot of contenders, and Aurios Media Bearings still win out. I imagine Rollerblocks would do OK too.
My next upgrade will be replacement of the output caps, but there's less available room relative to four being needed than for the two in the single-ended DAC, so my choices are fewer. Still contemplating that.
All the mods done to your DAC prior to you buying are good interventions. I'll just add that the WE 396A/2c51 is really a 396 as far as I can see, compared to a real Bendix or Tung-Sol 2c51. I encourage you to find one of those. The Bendix 6385 is allegedly the grail tube in these DACs, but I have found it slightly bleaching of tone, while giving very good definition. I may return to them for the Druid5 system DAC with the PCM56P-K. The 1964 Bendix 6385 is definitely not the best match to the AD1865. My real 2C51s are great with that chip.
Whether you will prefer the AD1865 in a single-ended Havana depends on the rest of your system and your hot buttons. Hard to predict without knowing more.
I am currently running my single ended Havana with the PCM56-K chip set and he WE396A. This is the best combination for the rest of my system. If I want to tighten up the presentation a bit some fun tubes to try are the vintage Russian 6H varieties such as the 6HNE, 6H3N-H or a 6H3N-AP. All of these all sound similar to each other and the best part is they only cost $2.00 each on ebay so you have nothing to lose.
Thanks Phil, I'll probalbly try the K chips.
System where the Havanna is as follows:
Cayin A-50T integrated with a full set of genelex gold lion toubes on input and output stages.
Havanna DAC being fed by Squeeze Box Touch with a welbourne labs power supply.
All ZU event cabling
Zu Essence upgraded to the HO drivers.
Hmm, why bust a gut getting this DAC to sound 'right'. Have any of you guys tried the Audio Note DACs? They are NOS and No filtering, and have tubed power supply and analogue boards.
Fir me, the NOS and no filtering is 70% of the signature i.e. no digital edge and an organic smooth sound. Then the quality of the supply and output stages and the sum of the parts is the remaining 30%.
I would recommend an Audio Note 2.1 Factory or an Audio Note 3.1 kit from Canada if you are a tweaker. The kits are great quality on a budget, and have LOTS of parts upgrade and circuit weak possibilities, aside form the tubes.
The mhdt Havana and Havana Balanced will go up against the Audio Note right out of the box. Being a DAC with a tube output buffer section, and the circuit supporting over a dozen tube variants, that happens to be an obvious variable to experiment with for tuning the sound. The fact that the chipset sockets support an additional variant is a further opportunity for voicing the DAC for those who care to try, but it's not necessary. The further upgrading of internal parts, particularly capacitors, is an area for modification in which the mhdt is neither more nor less susceptible to improvement than anything else, given that everything is built to a price point. But stock, Havana and Havana Balanced, as well as the Stockholm successors, are exceedingly fine DACs.
The last worthwhile thing even if you never open up the mhdt, or an Audio Note for that matter, is experimentation with what it sits on. But absolutely *every* DAC I've had my hands on is improved by finding the right support for dissipating internal vibration, and decoupling from external vibration, right up to 4 and 5 figures DACs, and the mhdt are no exception to this. For mhdt DACs, bearings-based supports are best.